What could have happened to Maura Murray? It’s a question that Tim Pilleri and Lance Reenstierna have been grappling with for years. Starting Sept. 23 at 8:15pm, Oxygen will begin airing "The Disappearance of Maura Murray," which stars Tim and Lance and hopes to make a break in the mysterious missing persons case.

Maura Murray, a 21-year-old nursing student, went missing 13 years ago. On February 9, 2004, the 21-year-old emailed her professors at University of Massachusetts and her employer requesting time off after death in her family. The death turned out to be made up. That night, she crashed her car into a tree in New Hampshire. A few witnesses called 911. When the police showed up, Maura was gone. When her dorm room was searched, campus police found most of her belongings packed in boxes and posters removed from the walls. Maura was never found. What could have happened?

Oxygen talked with Tim and Lance about some of the theories.

FOUL PLAY

“I think most people think she’s dead and we’ve learned that from certain polls that we’ve done,” said Tim. “I think probably the main theory is that she was met with foul play. I think that’s the most popular theory.”

In regards to that theory, Lance said that theorists often use the term “opportunistic serial killer,” which Lance says is inaccurate. ”If she was met with foul play it was someone who had potential to kill and saw the opportunity which is different than an opportunistic serial killer.”

Retired state police Lt. John Healy, an investigator who worked on the case, agrees with this theory. He told Mass Live that he thinks Maura was the victim of a "crime of opportunity."

"She got into the wrong car. She went to the wrong house," he said. "One minute she's there, 10 minutes later she's not."

RAN AWAY

Tim and Lance said that Maura started over and is living happily with a child, according to one hopeful theory. It’s the theory that they find the most interesting.

Lance said that theory consists of her running away from the men in her life and joining a women’s underground railroad, having a whole new identity set up for herself. According to that theory, Maura is somewhere out in the world living happily with a child. Some think she may have fled north, to Canada.

“I’d love that to happen and for us to be told privately that it happened and to keep our mouth shut,” said Lance.

DIED IN THE WOODS

“Another theory is that she was so stressed when she got into this car accident that she just took off and is in the woods still, like within a mile or two,” said Lance. “And they just never found her and she died of exposure but it was unseasonably warm that night and she would have gotten out of a couple mile radius for that to be true it think because of how extensive we were told the searches were.”

But Tim and Lance have differing views on whethere that theory is realistic. Since the police dogs lost her scent, one of them thinks that is evidence that she got into a car. The other thinks that the dogs didn’t get a good scent to begin with because they were given Maura’s gloves, which were given to her as a gift, items she may not have ever even worn. Her dad, Fred Murray, claimed she never put the gloves on.

INTERESTING PLAYERS

Nobody has officially been named a suspect in Maura’s disappearance, but here are some witnesses.

BUTCH ATWOOD

Butch Atwood was a school bus driver who lived nearby the scene of Maura’s crash. According to Mass Live, he may be the last person to have spoken to Maura. He told police that he asked Maura if she wanted him to call police. She said no, and told him that she called AAA. Butch apparently knew that was a lie because there was no cell service in the area. Butch called police anyway. He has since died.

“Witness A” is Karen McNamara, a witness that spoke to police about Maura’s disappearance. She agreed to be interviewed for both the show and the podcast.

BRIANNA MAITLAND

Some amateur sleuths believe that Maura Murray and Brianna Maitland were abducted by the same person. Brianna went missing in neighboring Vermont just one month after Maura vanished. She was 17 when she vanished in a simliar manner. She was never found but her car was found backed into the side of an abandoned house.